1. Field of the Invention
This invention relates to improvement in fuel cells. More particularly, the invention is concerned with a thin-film, high pressure fuel cell.
A fuel cell is a device in which energy from chemical reactions is made available as electric current.
An electrolyzer is a device wherein electrical energy is used to provide chemical reagents adapted to react chemically to regenerate electrical energy. When these devices are combined in a single package, the resulting device is a regenerative fuel cell.
2. Description of the Prior Art
The original concept for a regenerative electrochemical process in which electrical energy is the direct input and output of a chemical system can be traced to the work of "Grove" in 1839, and the principle of the fuel cell was formulated by W. Oswald as long ago as 1894.
However, only in recent years has there been any real progress in bringing the technology into any semblance of practicality. Thus, modern fuel cell development dates from the 1930's when F. T. Bacon developed a cell which operated on high-purity oxygen and hydrogen. Most developments from then have been modifications of the Bacon fuel cell.
Many of the prior art systems which utilize the H.sub.2 /O.sub.2 regenerative process employ electrodes which consist of porous media which provide a region where a three phase interface can exist in stable form (i.e., gas, liquid, solid) and catalytic electrochemical reaction can take place. These electrodes are expensive, physically unstable when used cyclically, subject to flooding, and limited in efficiencies at current densities of practical value. Thus, many prior art patents aimed at improving the nature of the electrodes. See, for examples, U.S. Pat. Nos. 2,716,670, 2,928,783, 2,969,315 and 3,167,457, all to Bacon.
By 1960 it was appreciated that temperature and pressure were significant to the performance of a fuel cell and A. M. Moos' "Fuel-Cells-Technical and Economic Study" SAE Paper 159D (April 1960) had shown the feasibility of cells operating at 600.degree. F. and 1000 psi.
A comprehensive review of fuel cell technology in 1960 is to be found in an article by F. T. Bacon entitled, "The High-Pressure Hydrogen-Oxygen Fuel Cell", appearing on pages 51-77 in "Fuel Cells" published by Reinhold (1960). In this article the author discusses the hydrogen-oxygen fuel cell using a potassium hydroxide electtrolyte and concludes that porous nickel is the best catalyst metal because of low cost, good corrosion resistance and superior performance under current drain. He discusses the improvement of cell performance with increased temperature and pressure up to 240.degree. C. and 1075 psi. Reference is made to cells which would withstand a pressure of 3000 psi but no performance data are given for such theoretical cells.
The article indicates that fuel cells of the type described have a number of advantages, for example: (1) the ability to take large overloads at reduced efficiency without damage; (2) silence and freedom from vibration in operation; (3) lack of moving parts; (4) the only waste material produced is water; and (5) the charging process merely consists of refilling with the two gases. However, it concludes that the application of such fuel cells is limited due to factors such as size and weight and possibly cost.